Day of Year or Julian Date?
Note that Julian date is sometimes used as a synonym for day of year, but this is not correct usage. Day of year ranges from 1 to 365 (366 for leap years) whereas Julian dates (abbreviated JD) are a continuous count of days and fractions since noon Universal Time on January 1, 4713 BCE (on the Julian calendar). Julian dates are widely used as time variables within astronomical software and should not be confused with day of year.
Day of Year Tables
Below are tables for determining the day of year for a given date.
Perpetual | Leap Years Only
Adobe PDF version of this calendar
| Day | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| 1 | 001 | 032 | 060 | 091 | 121 | 152 | 182 | 213 | 244 | 274 | 305 | 335 |
| 2 | 002 | 033 | 061 | 092 | 122 | 153 | 183 | 214 | 245 | 275 | 306 | 336 |
| 3 | 003 | 034 | 062 | 093 | 123 | 154 | 184 | 215 | 246 | 276 | 307 | 337 |
| 4 | 004 | 035 | 063 | 094 | 124 | 155 | 185 | 216 | 247 | 277 | 308 | 338 |
| 5 | 005 | 036 | 064 | 095 | 125 | 156 | 186 | 217 | 248 | 278 | 309 | 339 |
| 6 | 006 | 037 | 065 | 096 | 126 | 157 | 187 | 218 | 249 | 279 | 310 | 340 |
| 7 | 007 | 038 | 066 | 097 | 127 | 158 | 188 | 219 | 250 | 280 | 311 | 341 |
| 8 | 008 | 039 | 067 | 098 | 128 | 159 | 189 | 220 | 251 | 281 | 312 | 342 |
| 9 | 009 | 040 | 068 | 099 | 129 | 160 | 190 | 221 | 252 | 282 | 313 | 343 |
| 10 | 010 | 041 | 069 | 100 | 130 | 161 | 191 | 222 | 253 | 283 | 314 | 344 |
| 11 | 011 | 042 | 070 | 101 | 131 | 162 | 192 | 223 | 254 | 284 | 315 | 345 |
| 12 | 012 | 043 | 071 | 102 | 132 | 163 | 193 | 224 | 255 | 285 | 316 | 346 |
| 13 | 013 | 044 | 072 | 103 | 133 | 164 | 194 | 225 | 256 | 286 | 317 | 347 |
| 14 | 014 | 045 | 073 | 104 | 134 | 165 | 195 | 226 | 257 | 287 | 318 | 348 |
| 15 | 015 | 046 | 074 | 105 | 135 | 166 | 196 | 227 | 258 | 288 | 319 | 349 |
| 16 | 016 | 047 | 075 | 106 | 136 | 167 | 197 | 228 | 259 | 289 | 320 | 350 |
| 17 | 017 | 048 | 076 | 107 | 137 | 168 | 198 | 229 | 260 | 290 | 321 | 351 |
| 18 | 018 | 049 | 077 | 108 | 138 | 169 | 199 | 230 | 261 | 291 | 322 | 352 |
| 19 | 019 | 050 | 078 | 109 | 139 | 170 | 200 | 231 | 262 | 292 | 323 | 353 |
| 20 | 020 | 051 | 079 | 110 | 140 | 171 | 201 | 232 | 263 | 293 | 324 | 354 |
| 21 | 021 | 052 | 080 | 111 | 141 | 172 | 202 | 233 | 264 | 294 | 325 | 355 |
| 22 | 022 | 053 | 081 | 112 | 142 | 173 | 203 | 234 | 265 | 295 | 326 | 356 |
| 23 | 023 | 054 | 082 | 113 | 143 | 174 | 204 | 235 | 266 | 296 | 327 | 357 |
| 24 | 024 | 055 | 083 | 114 | 144 | 175 | 205 | 236 | 267 | 297 | 328 | 358 |
| 25 | 025 | 056 | 084 | 115 | 145 | 176 | 206 | 237 | 268 | 298 | 329 | 359 |
| 26 | 026 | 057 | 085 | 116 | 146 | 177 | 207 | 238 | 269 | 299 | 330 | 360 |
| 27 | 027 | 058 | 086 | 117 | 147 | 178 | 208 | 239 | 270 | 300 | 331 | 361 |
| 28 | 028 | 059 | 087 | 118 | 148 | 179 | 209 | 240 | 271 | 301 | 332 | 362 |
| 29 | 029 | | 088 | 119 | 149 | 180 | 210 | 241 | 272 | 302 | 333 | 363 |
| 30 | 030 | | 089 | 120 | 150 | 181 | 211 | 242 | 273 | 303 | 334 | 364 |
| 31 | 031 | | 090 | | 151 | | 212 | 243 | | 304 | | 365 |
If a year can be divided by 4 or 400 without remainder, it is a leap year.
If a year can be divided by 100 without remainder it is a common year.
The next leap year will be 2012.
The next year that is divisible by both 100 and 4 will be the year 2100.
The next year that is divisible by 400 will be the year 2400.
| Day | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| 1 | 001 | 032 | 061 | 092 | 122 | 153 | 183 | 214 | 245 | 275 | 306 | 336 |
| 2 | 002 | 033 | 062 | 093 | 123 | 154 | 184 | 215 | 246 | 276 | 307 | 337 |
| 3 | 003 | 034 | 063 | 094 | 124 | 155 | 185 | 216 | 247 | 277 | 308 | 338 |
| 4 | 004 | 035 | 064 | 095 | 125 | 156 | 186 | 217 | 248 | 278 | 309 | 339 |
| 5 | 005 | 036 | 065 | 096 | 126 | 157 | 187 | 218 | 249 | 279 | 310 | 340 |
| 6 | 006 | 037 | 066 | 097 | 127 | 158 | 188 | 219 | 250 | 280 | 311 | 341 |
| 7 | 007 | 038 | 067 | 098 | 128 | 159 | 189 | 220 | 251 | 281 | 312 | 342 |
| 8 | 008 | 039 | 068 | 099 | 129 | 160 | 190 | 221 | 252 | 282 | 313 | 343 |
| 9 | 009 | 040 | 069 | 100 | 130 | 161 | 191 | 222 | 253 | 283 | 314 | 344 |
| 10 | 010 | 041 | 070 | 101 | 131 | 162 | 192 | 223 | 254 | 284 | 315 | 345 |
| 11 | 011 | 042 | 071 | 102 | 132 | 163 | 193 | 224 | 255 | 285 | 316 | 346 |
| 12 | 012 | 043 | 072 | 103 | 133 | 164 | 194 | 225 | 256 | 286 | 317 | 347 |
| 13 | 013 | 044 | 073 | 104 | 134 | 165 | 195 | 226 | 257 | 287 | 318 | 348 |
| 14 | 014 | 045 | 074 | 105 | 135 | 166 | 196 | 227 | 258 | 288 | 319 | 349 |
| 15 | 015 | 046 | 075 | 106 | 136 | 167 | 197 | 228 | 259 | 289 | 320 | 350 |
| 16 | 016 | 047 | 076 | 107 | 137 | 168 | 198 | 229 | 260 | 290 | 321 | 351 |
| 17 | 017 | 048 | 077 | 108 | 138 | 169 | 199 | 230 | 261 | 291 | 322 | 352 |
| 18 | 018 | 049 | 078 | 109 | 139 | 170 | 200 | 231 | 262 | 292 | 323 | 353 |
| 19 | 019 | 050 | 079 | 110 | 140 | 171 | 201 | 232 | 263 | 293 | 324 | 354 |
| 20 | 020 | 051 | 080 | 111 | 141 | 172 | 202 | 233 | 264 | 294 | 325 | 355 |
| 21 | 021 | 052 | 081 | 112 | 142 | 173 | 203 | 234 | 265 | 295 | 326 | 356 |
| 22 | 022 | 053 | 082 | 113 | 143 | 174 | 204 | 235 | 266 | 296 | 327 | 357 |
| 23 | 023 | 054 | 083 | 114 | 144 | 175 | 205 | 236 | 267 | 297 | 328 | 358 |
| 24 | 024 | 055 | 084 | 115 | 145 | 176 | 206 | 237 | 268 | 298 | 329 | 359 |
| 25 | 025 | 056 | 085 | 116 | 146 | 177 | 207 | 238 | 269 | 299 | 330 | 360 |
| 26 | 026 | 057 | 086 | 117 | 147 | 178 | 208 | 239 | 270 | 300 | 331 | 361 |
| 27 | 027 | 058 | 087 | 118 | 148 | 179 | 209 | 240 | 271 | 301 | 332 | 362 |
| 28 | 028 | 059 | 088 | 119 | 149 | 180 | 210 | 241 | 272 | 302 | 333 | 363 |
| 29 | 029 | 060 | 089 | 120 | 150 | 181 | 211 | 242 | 273 | 303 | 334 | 364 |
| 30 | 030 | | 090 | 121 | 151 | 182 | 212 | 243 | 274 | 304 | 335 | 365 |
| 31 | 031 | | 091 | | 152 | | 213 | 244 | | 305 | | 366 |